Good morning. And welcome to "This week." Sabotage. Was Malaysia flight 370 hijacked? Did the pilots bring it down? More than a week after the plane vanished, investigators zero in on foul play, as a massive search continues this morning. We have all the breaking news from our global team. Also developing right now -- Russian troops mass on the Ukrainian border, before today's key vote in crimea. Will they invade Ukraine and split the country? We're live on the ground with the latest on the showdown between Putin and the west. Plus, the gop's warning shot in Florida. What is it like to be the last black president? And the president's health care hangover. All that, bill Gates, and the powerhouse "Roundtable," right here, this Sunday morning. From the moment Malaysia flight 370 signed off with a simple good night, it's been a mystery. Solving it now, a worldwide criminal investigation. Intense focus, this morning, on the pilots. But with no sign of motive, no claim of responsibility, nothing is being ruled out. And just hours ago, the Malaysian defense minister revealed that the search zone is actually expanding. So many questions this morning. And our team of correspondents and experts have all of the latest details and analysis, starting with ABC's David Kerley in Washington. David? Reporter: George, this map released by the Malaysian officials shows the possible arc locations of where flight 370 sent its last hourly transmission, which we now know happened seven hours after initial takeoff. Malaysia officials say they're searching both of these areas, both of the arcs, north and south, equally. But investigators say searchers will intently focus in the area off western Australia. Their hunt for this missing aircraft is a search area of at least 1,200 miles. Nine days and counting. And still, no physical sign of Malaysian air flight 370. But this weekend, confirmation from the Malaysian government that this mysterious disappearance was almost certainly no accident. These movements are consistent with deliberate action. Reporter: The prime minister confirming the report by ABC news, that communications gear was deliberately shut down. Now, we have learned from a source close to the investigation, that whoever was controlling the plane, preprogrammed that sharp left turn right off of the flight path. Convincing investigators that someone was in control of the jetliner. Either a rogue pilot or a hijacker. Someone taking command of this airplane or already having command and going rogue. And the intent is obviously lethal. Reporter: Radar confirming that the plane did fly back over the country. But then, what? Hourly satellite pings from the plane, which we learned can't be turned off, showed that flight 370 made another turn, before flying another six hours, far longer than first thought. But which direction did it turn? If it flew to the north, that would take it over land, towards Kazakhstan. Sources view this scenario as highly unlikely. But to the south, is open water. No radar over the Indian ocean, with depths up to 15,000 feet. And beyond that, Australia. That's where the search will be concentrated. We're going to have to have some luck to find this aircraft. The search area is so gigantic. Reporter: What then? Did the plane run out of fuel before crashing into the ocean? And more far-fetched, did the plane land under the cover of darkness? It's consistent with someone who wanted to vanish off the face of the Earth and make sure the ultimate crash site was never found. Reporter: While the search will have a higher profile here west of Australia, in the southern Indian ocean, all of the moves to shut off cockpit communication systems, the major changes of direction, all those things are bringing in new scrutiny to the two pilots. George? Thanks. We want to get more on the criminal investigation from our senior justice correspondent, Pierre Thomas. He's in Washington, as well. Good morning, Pierre. Reporter: Good morning, George. Finding everything there is to know about the pilots is clearly a top priority. Within a week after the plane's disappearance, authorities searched the homes of the captain and co-pilot of the now-infamous Malaysian airlines flight. I was shocked they waited so long to do it. Reporter: Malaysian authorities confirm they are still investigating all passengers. These two men are one of the primary focuses of the early international investigation. The reason, authorities say the plane did a series of maneuvers. And there may have been an attempt to avoid radar. So far, U.S. Intelligence has found no evidence any of the other passengers or crew had any flight training or skill. I look at the pilots first, obviously. They're in the cockpit. I get their information. But given the lack of information we have, I start looking at who else we have on the airplane. Reporter: There's an urgent effort to see if the pilots had any ties to extremist or psychological issues that could make them commandeer the plane. You do an initial assessment of their life. Religion, athletics, social events, social clubs. In other words, how do they spend their time? Reporter: But there are still many questions. The captain is described as a family man who works for charity. Someone who would never hurt passengers. And the authorities have to resolve whether one of the passengers could have forced one of the pilots to hijack the plane. Or had flight training yet to uncover. Pilots have been accused of intentionally downing planes before. U.s. Investigators concluded the co-pilot of an Egypt air flight intentionally ran the plane into the atlantic ocean in 1999. In 1997, a pilot from Singapore was accused of crashing his plane into a river. The U.S. Investigation has not yet found anyone onboard that has ties to terrorist organizations. And sources point out that once the plane was redirected, whoever took control, had ample activity to crash a huge aircraft into populated areas and did not. The FBI still has not been invited inside the country to help.

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